A research team has uncovered that specific sleep patterns may influence the risk of developing Alzheimer's disease, depending on genetic variations related to the glymphatic system. The study, published in the scientific journal Alzheimer's and Dementia, focused on aquaporin-4 (AQP4), a crucial water channel in the glymphatic system. This system is responsible for clearing waste from the brain during sleep. The researchers from Edith Cowan University analyzed 351 older adults, on average 75 years old, who had normal memory at the start of the study but showed high levels of amyloid beta in brain scans—a known early sign of Alzheimer's risk. The participants completed a sleep survey, underwent cognitive tests, and had MRI and PET scans to assess brain structure and function. Thirteen common variants of the AQP4 gene were analyzed. The team found that individuals carrying a variant called rs162007 had better memory and thinking scores at the beginning of the study, regardless of their sleep habits. In a healthy brain, the glymphatic system functions like an internal plumbing system, circulating cerebrospinal fluid through the brain’s vessels to remove amyloid beta and other waste. The AQP4 protein, found on astrocytes—specialized brain cells—acts as a gateway to this process. This "nightly washing" is most active during deep, slow-wave sleep. When this sleep is lacking, toxic proteins can accumulate, eventually leading to the brain changes seen in Alzheimer's disease. For some AQP4 variants (rs151245 and rs2339214), shorter sleep duration was linked to a faster loss of gray matter over the years. "Our study shows that people carrying certain AQP4 variants showed a faster loss of gray matter when they reported sleeping less," said Ayeisha Milligan Armstrong, as reported by PsyPost. Among participants without these genetic profiles, shorter sleep was not associated with faster brain shrinkage. "It's not just the genes you carry, it's how these genes interact with the world around you," she explained. "The same variant can seem protective or harmful depending on how a person sleeps," she added. The researchers also examined cerebral ventricles—fluid-filled cavities in the brain that expand when surrounding tissue shrinks. A longer sleep duration was linked to larger ventricles in carriers of the rs7240333 variant, while poor sleep quality predicted faster expansion of these ventricles in those with rs2339214. Another variant, rs68006382, was associated with lower white matter volumes when sleep duration increased. "This is important, because sleep is one of the few modifiable factors on which people can really act," said Ayeisha Milligan Armstrong. Surprisingly, some rare genetic profiles (rs12968026 and rs3875089) appeared to offer a protective effect: in these individuals, more nighttime awakenings were linked to a slower decline in cognitive abilities. While it is known that poor sleep is connected to Alzheimer's risk, Tenielle Porter told PsyPost that this study suggests a more personalized approach to prevention may be necessary. However, the researchers did not find a clear link between these AQP4 variants and the progression of amyloid beta levels over time, suggesting the most significant effects might occur decades earlier. The observed differences in brain volume and performance are relatively small and do not yet allow for predicting an individual's future. "But we are not at the point of recommending genetic tests; our results need to be reproduced in larger and more diverse groups," clarified Tenielle Porter.